LONDON: Prince William and his wife Kate's second child, who will be fourth in line to the British throne, is due in April, an official statement said on Monday.

“Their Royal Highnesses The Duke and Duchess of Cambridge are delighted to confirm they are expecting a baby in April 2015,” said a statement from the couple's official residence, Kensington Palace.

It also said the 32-year-old pregnant duchess will make her first public appearance in more than two months on Tuesday at a ceremony in honour of Singaporean President Tony Tan.

The duchess was last seen at a ceremony at the Tower of London on August 5 in honour of World War I victims and has been suffering from acute morning sickness.

The couple announced they were expecting last month and she has been forced to cancel several engagements since then, including a trip to Malta on what would have been her first solo foreign tour.

The prince's grandmother Queen Elizabeth II has said she is “delighted” at the news, which comes just over a year after the birth of the couple's first child, Prince George.

Kate has been suffering from 'hyperemesis gravidarum', a form of very acute morning sickness that caused her to be hospitalised when she was pregnant with George.

William has said he is “thrilled” about the new baby.

Kate has been increasing her public profile since she married William in a lavish ceremony in April 2011.

A “commoner” by birth who met the prince at university in Scotland, she appears to have moved effortlessly into her royal role and has become hugely popular with the public, as well as a global style icon.

But the couple have worked hard to keep their family life private after the press interest in William's mother Diana, who was killed in a car crash in Paris in 1997 as her vehicle was chased by paparazzi.

They sent a legal warning letter earlier this month to a photographer who was trying to take pictures of toddler George with his nanny.

A spokesman for the duke and duchess said the photographer may have been carrying out “surveillance” of the prince's daily routines and said the baby had to be “removed” from a central London park when the photographer in question got too close.